U.S. patent application number 13/061194 was filed with the patent office on 2011-08-25 for method and system for acquiring and repatriating satellite data.
This patent application is currently assigned to CENTRE NATIONAL D'ETUDES SPATIALES (CNES). Invention is credited to Jean-Pierre Antikidis, Jean-Jacques Favier.
Application Number | 20110206096 13/061194 |
Document ID | / |
Family ID | 40386521 |
Filed Date | 2011-08-25 |
United States Patent
Application |
20110206096 |
Kind Code |
A1 |
Antikidis; Jean-Pierre ; et
al. |
August 25, 2011 |
METHOD AND SYSTEM FOR ACQUIRING AND REPATRIATING SATELLITE DATA
Abstract
A method of acquiring and repatriating satellite data
representative of a zone in space, termed the target zone, and an
instrument for acquiring and repatriating satellite data including
a plurality of satellites (1, 100), a plurality of terrestrial
receiving stations (50, 51, 52, 53, 54), the instrument includes,
for each item of data received by a receiving station (50, 51, 52,
53, 54), termed the receiving station, originating from the space
layer: elements for determining a receiving station (50, 51, 52,
53, 54) intended for storing this item of data, termed the
receiving station competent in respect of this item of data, and a
terrestrial digital network for routing this item of data from the
station receiving this item of data to the receiving station
competent in respect of this item of data.
Inventors: |
Antikidis; Jean-Pierre;
(Castanet, FR) ; Favier; Jean-Jacques; (Montastruc
la Conseillere, FR) |
Assignee: |
CENTRE NATIONAL D'ETUDES SPATIALES
(CNES)
Paris Cedex 01
FR
|
Family ID: |
40386521 |
Appl. No.: |
13/061194 |
Filed: |
August 20, 2009 |
PCT Filed: |
August 20, 2009 |
PCT NO: |
PCT/FR2009/051613 |
371 Date: |
April 12, 2011 |
Current U.S.
Class: |
375/211 |
Current CPC
Class: |
H04B 7/18578
20130101 |
Class at
Publication: |
375/211 |
International
Class: |
H04B 7/185 20060101
H04B007/185 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 2008 |
FR |
0804744 |
Claims
1-16. (canceled)
17. Process for acquisition and downloading of satellite data
pertaining to a zone of space, named the target zone, in which:
data are acquired by a constellation of satellites, named the
spatial layer, each satellite being equipped with at least one
device for acquisition of data, the data are transmitted to a
plurality of receiving stations distributed over the surface of the
globe, named the terrestrial layer, each receiving station
including at least one receiving module for receiving data and
storage means for storage of received data, wherein, for each datum
received by a receiving station, named the receiver station, and
emanating from said spatial layer: a receiving station intended to
store this datum, named the competent receiving station, is
determined by determination means, this datum is stored by said
storage means of said receiver station of this datum if this
receiver station is the competent receiving station for this datum,
this datum is routed, by means of a terrestrial digital network
interlinking the receiving stations with each other, from said
receiver station to said competent receiving station for this datum
if said receiver station of this datum is not said competent
receiving station for this datum.
18. The process as claimed in claim 17, wherein, for each receiving
station, characteristic data define a not necessarily continuous
portion of said target zone, named the circle of visibility of this
receiving station, for which this receiving station is competent,
data received by said receiving module of this receiving station
are selected by a selection module if these data pertain to said
circle of visibility of this station, and are circulated over said
terrestrial digital network if they are not selected by said
selection module.
19. The process as claimed in claim 18, wherein said characteristic
data defining said circle of visibility of each receiving station
are stored in a memory that can be accessed by said selection
module of this receiving station.
20. The process as claimed in claim 19, wherein, for each receiving
station, said memory of this receiving station, which includes said
characteristic data that define said circle of visibility of this
receiving station, can be accessed remotely by means for remote
access.
21. The process as claimed in claim 17, wherein said terrestrial
digital network is a public digital network.
22. The process as claimed in claim 17, wherein said target zone is
the terrestrial globe.
23. The process as claimed in claim 18, wherein said data stemming
from said spatial layer are digital images.
24. The process as claimed in claim 23, wherein, for each image
received by each receiving station, data that are representative of
the spatial and temporal coordinates of this image which are stored
in the header of the image received by said selection module of
this receiving station are read by reading means.
25. Instrument for acquisition and downloading of satellite data
that are representative of a zone of space, named the target zone,
comprising: a plurality of satellites named the spatial layer for
acquisition of data, each satellite being equipped with at least
one device for acquisition of data pertaining to at least one
portion of said target zone, and with means for transmission of the
acquired data to the ground, a plurality of terrestrial receiving
stations, named the terrestrial layer, each receiving station
including a module for receiving data stemming from said spatial
layer and means for storage of data stemming from said spatial
layer, wherein said instrument includes: for each datum received by
a receiving station, named the receiver station, and emanating from
said spatial layer, means for determination of a receiving station
intended to store this datum, named the competent receiving station
for this datum, a terrestrial digital network interlinking the
receiving stations with each other, so that a datum received by a
receiver station that is not said competent receiving station for
this datum can be routed by means of this terrestrial digital
network to the competent receiving station for this datum.
26. The instrument as claimed in claim 25, wherein said means for
determination of a competent receiving station include, for each
receiving station: characteristic data defining a not necessarily
continuous portion of said target zone, named the circle of
visibility of this receiving station, for which this receiving
station is said competent receiving station, a selection module for
selection of data received by said receiving module of this station
that is suitable to select the data that pertain to said circle of
visibility of this station and to circulate over said terrestrial
digital network all the data received by its receiving module not
selected by said selection module.
27. The instrument as claimed in claim 26, wherein each receiving
station includes, in a memory that can be accessed by said
selection module, said characteristic data that define said circle
of visibility of this receiving station.
28. The instrument as claimed in claim 27, wherein it includes, for
each receiving station, means for remote access to said memory of
this receiving station which includes said characteristic data that
define said circle of visibility of this receiving station.
29. The instrument as claimed in claim 25, wherein said terrestrial
digital network is a public digital network.
30. The instrument as claimed in claim 25, wherein said target zone
is the terrestrial globe.
31. The instrument as claimed in claim 26, wherein said data
stemming from said spatial layer are digital images.
32. The instrument as claimed in claim 31, wherein said selection
module for selection of data of each receiving station includes
means for reading the header of each image that are suitable to
read data that are representative of the spatial and temporal
coordinates of this image.
33. The instrument as claimed in claim 25, wherein said data
stemming from said spatial layer are digital images.
34. The process as claimed in claim 17, wherein said data stemming
from said spatial layer are digital images.
Description
[0001] The invention concerns a process for acquisition and
downloading of satellite data that are representative of a zone of
space. The invention also concerns an instrument for acquisition
and downloading of satellite data that are representative of a zone
of space. More particularly, the invention concerns a process for
downloading of images to the Earth and an instrument for
terrestrial observation.
[0002] An instrument for terrestrial observation is known
comprising: [0003] a constellation of satellites, named the spatial
layer for acquisition of images, each satellite being equipped with
at least one optical device for acquisition of images of portions
of the terrestrial globe and including at least one module for
transmission of the acquired images to a terrestrial layer, [0004]
a plurality of receiving stations distributed over the surface of
the globe, named the terrestrial layer, each receiving station
including at least one module for receiving images stemming from
the spatial layer.
[0005] The SPOT constellation of satellites constitutes such an
instrument. This constellation comprises a plurality of satellites
placed in a heliosynchronous, circular, polar orbit and in phase in
relation to the Earth. Each satellite has a cycle of 26 days. Each
satellite includes optical instruments, data recorders and systems
for transmission of the images to receiving stations on the ground.
The optical instruments are suitable to ensure parameterisable
oblique aims, so that the same region can be observed several times
in the course of the cycle of 26 days. The data recorders enable
the images to be stored on board if the satellite is not in the
line of sight of a ground station. When a satellite is in the line
of sight of a ground station, it transmits, by means of a module
for transmission of images, the images stored in the on board
recorders to the ground station. Each ground station, in turn, then
transmits the images to a central server for processing and storage
of the images. The same occurs with many other known instruments,
for example the Landsat constellation.
[0006] One drawback of such an instrument lies in the cost of
manufacture, installation, management and maintenance of the
constellation of satellites, of the ground stations and of the
central server. In particular, such an instrument necessitates the
installation and management on the ground of a plurality of ground
stations operated in autonomous manner in relation to one another
and suitable to send the received images to a central server for
backup of the images in a view of their distribution to users.
[0007] Furthermore, such an instrument comes up against a major
practical difficulty in the case where it is sought to obtain a
coverage of the whole of the terrestrial globe by images that
exhibit a spatial resolution of the order of one meter and a
frequency of global coverage of the order of one day. Such a
coverage compels management by the central server of around 1500
terabytes of data per day, that is to say, 170 gigabytes per
second, largely exceeding the capacities of satellite transmission
and ground processing that are attainable with the technologies and
architectures of the servers currently available.
[0008] The invention aims to overcome these drawbacks and to
provide an instrument for acquisition and downloading of satellite
data that enables the acquisition and downloading of a large amount
of data.
[0009] The invention also aims to provide such an instrument that
does not necessitate a central server for processing and backup of
the data.
[0010] To this end, the invention concerns an instrument for
acquisition and downloading of satellite data that are
representative of a zone of space, named the target zone,
including: [0011] a plurality of satellites, named the spatial
layer for acquisition of data, each satellite being equipped with
at least one device for acquisition of data pertaining to at least
one portion of said target zone, and with means for transmission of
the acquired data to the ground, [0012] a plurality of terrestrial
receiving stations, named the terrestrial layer, each receiving
station including a receiving module for receiving data and storage
means for storage of data, wherein it includes: [0013] for each
datum received by a receiving station, named the receiver station,
and emanating from said spatial layer, means for determination of a
receiving station intended to store this datum, named the competent
receiving station for this datum, [0014] a terrestrial digital
network interlinking the receiving stations with each other, so
that a datum received by a receiver station that is not the
competent receiving station for this datum can be routed by means
of this terrestrial digital network to the competent receiving
station for this datum if said receiver station for this datum is
not said competent receiving station for this datum.
[0015] Throughout the text, and for each datum stemming from the
spatial layer, a receiving station is said to be the receiver for
this datum if it receives this datum directly from one of the
satellites of the spatial layer, and a receiving station is said to
be competent for this datum if this datum is intended to be stored
by this receiving station. And to be kept stored by this competent
receiving station. Satellite datum stemmed from the spatial layer
are thus stored in a distributed form within the different
competent receiving stations, and in particular they are not
centralized in a central site as in the prior instruments such as
Spot or Landsat. A receiving station may be receiver station and
competent receiving station for a datum in the case where the
receiving station that directly receives the datum from the spatial
layer is also intended to store this datum.
[0016] The terrestrial digital network constitutes means for
routing each datum from a receiver station to the competent
receiving station for this datum.
[0017] An instrument according to the invention enables a
downloading of data from the spatial layer to the terrestrial layer
which may be not only direct--a satellite sends the acquired datum
directly to the competent receiving station for storing this
image--but also indirect--a satellite sends an acquired datum to a
receiving station that is not competent for this datum, and the
terrestrial digital network then enables this datum to be routed
from this non-competent receiver station to the receiving station
that is competent for this datum.
[0018] Such a mixed downloading of data--direct and indirect--makes
it possible for each datum acquired by the spatial layer to follow
a non-systematic opportunist path. In other words, if the datum can
be downloaded along a direct path to its competent receiving
station for this datum--taking account, notably, of the load of
this receiving station, its condition (in working condition or
otherwise), the atmospheric conditions, etc.--the datum takes this
direct path between the satellite and this competent receiving
station. On the other hand, if direct downloading is not possible
the datum then takes an indirect path constituted by a transfer
between the satellite and a receiver station and a subsequent
transfer between the receiver station and the competent receiving
station for this datum by means of the terrestrial digital
network.
[0019] Advantageously and according to the invention, the
terrestrial digital network is a public digital network. Such a
network is advantageously IP-compatible and is, for example, the
Internet network. The ground link between the receiver station of a
datum for which it is not competent and the competent receiving
station therefore advantageously utilises the principle of the IP
protocol. The datum is circulated over the network and is
propagated from station to station until a receiving station
recognises this datum as a datum for which it is competent and
which is therefore intended for it.
[0020] For each datum received by the terrestrial layer, means for
determination of a competent receiving station for this datum
designate such a competent receiving station. These determination
means may be of all types. They may, for example, determine the
competence of a station as a function of a characteristic that is
peculiar to the datum, each station being competent for data
exhibiting certain common peculiar characteristics. For example,
the characteristic of the datum determining competence may be a
characteristic linked to the geographical zone covered by this
datum, so that a competent receiving station for this
characteristic will receive, directly or indirectly, all the data
corresponding to this zone. The characteristic of the datum
determining competence may also be a characteristic linked to the
type of instrument having acquired this datum, so that a competent
receiving station for these data will receive, directly or
indirectly, all the data acquired by instruments of this type. In
the case of image data the characteristic of the datum determining
competence may be linked to a mean level of grey of the image, to a
predetermined range of spatial frequencies, to a predetermined
texture, and in general manner to all types of characteristics
capable of being extracted from an image by image-processing means.
In this case all the images exhibiting similar mean levels of grey,
similar spatial frequencies, similar textures, etc. are routed,
directly or indirectly, to the same competent receiving station.
The characteristic determining competence may also correspond to a
date and/or to a time of acquisition of the datum, so that, for
example, all the data acquired in the same time-slot each day are
routed to the same receiving station in order to be stored by this
competent receiving station. In general manner, the determination
means make it possible to distinguish the data received by the
terrestrial layer in such a manner that the data exhibiting similar
peculiar characteristics are stored by the same receiving station.
Advantageously and according to the invention, the competence of a
receiving station is a function of a geographical zone covered by
the data. This zone is a portion of the target zone, of which the
instrument according to the invention acquires and downloads data.
This geographical zone which determines the competence of a
receiving station is named the circle of visibility of this
receiving station. This zone is not necessarily continuous, so a
receiving station may be competent for a set of geographical zones
that are disjoint from one another.
[0021] Said determination means may be physically distinct from the
receiving stations. Thus they may, for example, include a central
server that is linked to the set of the receiving stations of the
terrestrial layer and that is suitable to establish, for example
from a correspondence table, the competent receiving station for
each datum, taking account of a characteristic linked to this
datum.
[0022] Nevertheless, advantageously and according to the invention,
said determination means include, for each receiving station:
[0023] characteristic data defining a not necessarily continuous
portion of said target zone, named the circle of visibility of this
receiving station, for which this receiving station is the
competent receiving station, [0024] a selection module for
selection of data received by said receiving module of said
receiving station, which is configured to select the data that
pertain to said circle of visibility of said receiving station and
to circulate over said terrestrial digital network all the data
received by its receiving module that are not selected by said
selection module.
[0025] According to this embodiment variant, said determination
means are, at least in part, localised in each receiving station.
In particular, each receiving station includes a module for
selection of data received by the receiving module of this
receiving station, which is suitable to select the data that
correspond to the circle of visibility of this station. If the
datum received by this station is not within its competence, then
this datum is placed onto the terrestrial digital network
interlinking the receiving stations with each other so that it can
be routed to the competent receiving station for this datum.
According to this variant, the receiving module of each receiving
station is suitable not only to receive the data directly from the
spatial layer but also to receive the data from the terrestrial
digital network, so that the selection module can also analyse the
data stemming from the digital network in order to define whether
this datum is within the competence of this receiving station or
has to be replaced onto the network. In this way this datum is
conveyed, step by step, over the terrestrial digital network until
it reaches its competent receiving station.
[0026] According to another variant, and as pointed out previously,
a selection module can select the data as a function of
characteristics other than their membership of the circle of
visibility of the station, such as, for example, the instrumental
origin of this datum, the time of acquisition, etc.
[0027] In the case where the competence is a function of the
geographical zone covered by the datum, advantageously and
according to the invention each receiving station includes, in a
memory that can be accessed by said selection module, the
characteristic data that define said circle of visibility of this
receiving station. The circle of visibility is defined locally in
each receiving station.
[0028] In addition, an instrument according to the invention
advantageously includes, for each receiving station, means for
remote access to said memory of this receiving station which
includes said characteristic data that define said circle of
visibility of this receiving station. According to this variant, an
operator may, if necessary, easily remotely redefine the competence
of each receiving station by modifying the characteristic data that
define the circle of visibility of this receiving station and
therefore its competence. This may, for example, be useful in case
of addition to the instrument of one or more receiving stations
with a view, notably, to distributing the acquired data better
among all the receiving stations of the terrestrial layer. This may
also be useful in case of a redefinition of the target zone
observed by the instrument that would have the consequence of
enlarging the zone observed by the instrument and therefore of
increasing the amount of data transmitted to the terrestrial
layer.
[0029] This target zone may be of all types. In particular, an
instrument according to the invention can be used for the
acquisition and downloading of images of the celestial canopy.
According to this embodiment, the satellites carry instruments for
acquisition of images, and each instrument is oriented towards the
stars in such a way as to acquire a zone of the sky. The images can
then be downloaded to the terrestrial layer and can be distributed
as a function of the zone of the universe covered by each image.
According to this embodiment, a receiving station may be competent
for all the images that correspond to a given galaxy or to a type
of particular celestial objects being observed, etc.
[0030] Advantageously and according to the invention, the target
zone is the terrestrial globe. According to this embodiment, the
instrument is an instrument for acquisition and downloading of
observation data pertaining to the earth.
[0031] The data stemming from said spatial layer are preferably
digital images. Such an instrument enables the acquisition and
downloading of images of the terrestrial globe. According to this
embodiment, the competence of a receiving station is preferably
associated with a zone of the globe.
[0032] According to this embodiment, a mixed downloading of the
images enables the instrument to acquire images of zones that do
not include a receiving station, such as sea zones, while enabling
their downloading to a competent receiving station for these zones.
Such a competent receiving station exhibits a circle of visibility
that encompasses all or some of the images of the sea. This also
makes it possible to attribute to a given receiving station, for
example the competent station for the images of Paris, the
processing and accommodation of the images of Corsica. In other
words, competence for Corsica is attributed to the competent
receiving station for Paris. Consequently, all the images of
Corsica are routed to the competent station for Paris by an
indirect downloading.
[0033] According to this variant, each received image is
transmitted to a selection module that is suitable to determine
whether or not this image is an image that pertains to the circle
of visibility of this receiving station. The determination of this
membership may be effected in various ways. Nevertheless,
advantageously and according to the invention, the selection module
for selection of images of each receiving station includes means
for reading the header of each image that are suitable to read the
data that are representative of the spatial and temporal
coordinates of this image. These spatial and temporal coordinates
of the image are inserted into the header of the image by the
satellite that captures the image. In fact, each satellite of the
spatial layer knows the time at which the image is acquired by its
device for acquisition of images, as well as the coordinates of the
image that it acquires.
[0034] According to this embodiment, each receiving station stores
locally the images for which it is competent.
[0035] To a receiving station of an instrument according to the
invention there may be attributed in this way the processing and
backup of zones of the globe that are geographically remote from
the physical location of the receiving station. The corresponding
images are routed to the competent station by an indirect
downloading as described above. In this way, the parameterisation
of the circle of visibility of a receiving station enables this
station to be rendered competent for any zone of the globe. In
addition, with an instrument according to the invention it is easy
to change the competence of a receiving station. This changing of
competence consists in changing the definition of its circle of
visibility--that is to say, in modifying the data, stored in said
memory which can be accessed by the selection module, that are
representative of the circle of visibility.
[0036] The invention also concerns a process for acquisition and
downloading of satellite data pertaining to a zone of space, named
the target zone, in which: [0037] data are acquired by a
constellation of satellites, named the spatial layer, each
satellite being equipped with at least one device for acquisition
of data, [0038] the data are transmitted to a plurality of
receiving stations distributed over the surface of the globe, named
the terrestrial layer, each receiving station including at least
one receiving module for receiving data and storage means for
storage of received data, wherein, for each datum received by a
receiving station, named the receiver station, and emanating from
said spatial layer: [0039] a receiving station intended to store
this datum, named the competent receiving station, is determined by
determination means, [0040] this datum is stored by said storage
means of said receiver station of this datum if this receiver
station is the competent station for this datum, [0041] this datum
is routed, by means of a terrestrial digital network interlinking
the receiving stations with each other, from said receiver station
to said competent receiving station for this datum if said receiver
station of this datum is not said competent receiving station for
this datum.
[0042] A process for acquisition and downloading of data according
to the invention enables a downloading of the data from the spatial
layer to a receiving station of the terrestrial layer that may be
direct or indirect.
[0043] According to a variant of the invention, the process
according to the invention concerns the acquisition and downloading
of terrestrial observation images. According to such a process for
acquisition and downloading of images of the terrestrial globe:
[0044] images of the globe are captured by a constellation of
satellites, each satellite being equipped with at least one optical
device for acquisition of images and including at least one module
for transmission of images, [0045] the images are transmitted to a
plurality of receiving stations distributed over the surface of the
globe, each receiving station including at least one module for
receiving images, characterised in that: [0046] each image received
by a receiving module of a receiving station is analysed by a
selection module that is configured to select an image of a
predetermined geographical zone, named the circle of visibility of
the receiving station, [0047] each image not selected by said
selection module is transmitted to a terrestrial digital network
that interlinks the receiving stations, so that it can reach the
competent receiving station for this image by a ground link.
[0048] Advantageously and according to the invention, for each
receiving station, [0049] characteristic data define a not
necessarily continuous portion of said target zone, named the
circle of visibility of this receiving station, for which this
receiving station is competent, [0050] data received by said
receiving module of this receiving station are selected by a
selection module if these data pertain to said circle of visibility
of this station, and are circulated over said terrestrial digital
network if they are not selected by said selection module.
[0051] Advantageously and according to the invention, said
characteristic data defining said circle of visibility of each
receiving station are stored in a memory that can be accessed by
said selection module of this receiving station.
[0052] Advantageously and according to the invention, for each
receiving station said memory of this receiving station, which
includes said characteristic data that define said circle of
visibility of this receiving station, is accessible remotely by
means for remote access.
[0053] Advantageously and according to the invention, said
terrestrial digital network is a public digital network.
[0054] Advantageously and according to the invention, said target
zone is the terrestrial globe.
[0055] Advantageously and according to the invention, said data
stemming from said spatial layer are digital images.
[0056] Advantageously and according to the invention, for each
image received by each receiving station, data that are
representative of the spatial and temporal coordinates of this
image which are stored in the header of the image received by said
selection module of this receiving station are read by reading
means.
[0057] The invention also concerns an instrument for acquisition
and downloading of satellite data and a process for acquisition and
downloading of satellite data, characterised in combination by all
or some of the characteristics mentioned above or below.
[0058] Other objectives, characteristics and advantages of the
invention will become apparent from the following description which
is given solely by way of non-limiting example and which refers to
the appended Figures, in which:
[0059] FIG. 1 is a schematic view of a portion of an instrument for
acquisition and downloading of satellite data according to an
embodiment of the invention,
[0060] FIG. 2 is a schematic view according to another
representation of an instrument for observation of the terrestrial
globe according to an embodiment of the invention,
[0061] FIG. 3 is a schematic view of an instrument according to an
embodiment of the invention that represents a direct downloading of
an image from a satellite to a competent receiving station for this
image,
[0062] FIG. 4 is a schematic view of an instrument according to an
embodiment of the invention that represents an indirect downloading
of an image from a satellite to a competent receiving station for
this image by means of receiving stations that are not competent
for this image,
[0063] FIG. 5 is a schematic view of a satellite and of a receiving
station of an instrument according to an embodiment of the
invention.
[0064] In the Figures, the scales and the proportions are not
strictly respected, for purposes of illustration and clarity.
[0065] FIG. 1 is a very schematic view of a portion of an
instrument according to the invention. In this Figure, an
instrument for acquisition and downloading of satellite data that
are representative of a zone of space, named the target zone,
includes a plurality of satellites 1, 100 and a plurality of
terrestrial receiving stations 50, 51, 52. In addition, such an
instrument includes, for each datum received by a receiving station
50, 51, 52, determination means 22 for determination of a receiving
station 50, 51, 52 intended to store this datum, named the
competent receiving station for this datum, and means for routing
this datum from said receiver station of this datum to said
competent receiving station for this datum. These routing means are
constituted by a terrestrial digital network 20. Such a terrestrial
digital network 20 ensures the circulation of data between the
various stations by essentially terrestrial means. According to a
preferential embodiment, this terrestrial digital network 20 is a
public digital network such as the Internet network.
[0066] The determination means 22 may be of all types. They may,
for example, determine the competence of a station as a function of
a characteristic that is peculiar to the datum, each station being
competent for data exhibiting certain common peculiar
characteristics. In addition, these determination means 22 may be
physically distinct from the receiving stations. Thus they may, for
example, include a central server linked to the set of the
receiving stations and suitable to establish, for example from a
correspondence table, the competent receiving station for each
datum, taking account of a characteristic linked to this datum.
According to a preferential embodiment represented notably in FIG.
5, these determination means 22 are incorporated into each
receiving station and include, for each receiving station 50, 51,
52, 53, 54, characteristic data defining a portion of said target
zone, named the circle of visibility of this receiving station, for
which this receiving station is competent, and a selection module
11 for selection of data received by a receiving module 12 of this
station that is suitable to select the data that pertain to said
circle of visibility of this station and to supply to the digital
network 20 all the data received by its receiving module that are
not selected by said selection module, so that they can be routed
to their corresponding competent receiving station.
[0067] The embodiment shown in the Figures concerns an instrument
for acquisition and downloading of images of observation of the
terrestrial globe. Starting from this embodiment that has been
described, a person skilled in the art will be able, without
difficulty, to realise an instrument for acquisition and
downloading of other types of data, such as, for example, radar
data pertaining to celestial objects.
[0068] According to this embodiment, each satellite includes at
least one optical device 2 for acquisition of images and a module 4
for transmission of images to the ground. The optical device 2 for
acquisition of images may be of all known types. Nevertheless,
according to a preferential embodiment such an optical device 2 is
a camera with fixed aim oriented towards the Earth and suitable to
acquire multispectral images of the terrestrial regions that this
satellite 1 overflies. Such an optical device 2 with fixed aim does
not therefore, by definition, permit losses of aim. A satellite 1
of an instrument according to the invention therefore does not
necessitate a particular aiming programme, significantly reducing
the costs of manufacture and maintenance.
[0069] The satellites 1 may, for example, be optical parachutes.
These satellites 1 preferably exhibit a low orbit, so that they can
describe a large number of orbits in one day. Each satellite 1 of
an instrument according to the invention preferably executes more
than one orbit in one day. According to an embodiment of the
invention, each satellite 1 executes sixteen orbits in one day.
[0070] The transmission module 4 for transmission of images of a
satellite 1 of an instrument according to the invention is suitable
to transmit the images to the ground.
[0071] Such a transmission module 4 may be of all known types and
is not described here in detail. According to a particularly
advantageous embodiment of the invention, each satellite 1
includes, as represented in FIG. 5, a compression module 3 for
compression of images, which is arranged between the device 2 for
acquisition of images and the module 4 for transmission of images
to a receiving station 50, so that each image acquired by the
device 2 for acquisition of images can be compressed by this
compression module 3 before being transmitted to the Earth by the
module 4 for transmission of images.
[0072] Each receiving station 50, 51, 52, 53, 54 includes,
according to a preferential embodiment of the invention, a module
10 for receiving images, a module 11 for selection of images, and a
memory 12 that can be accessed by the selection module 11. This
memory 12 includes data that are representative of the geographical
zones that constitute the circle of visibility of this receiving
station and therefore make it possible to parameterise this circle
of visibility. A receiving station is said to be competent for a
received image if it corresponds to a geographical zone defined by
the data of the memory 12. Moreover, each receiving station 50, 51,
52, 53, 54, 55, 56 includes storage means 13 for storage of the
received images that are part of the circle of visibility of this
receiving station. These storage means 13 may be of all types, for
example a mass memory such as a disc memory.
[0073] According to the invention, the receiving stations 50, 51,
52, 53, 54 are interlinked with each other by a digital network 20,
so that each receiving station 50, 51, 52, 53, 54 can circulate
over this digital network 20 all the images received by its
receiving module 10 that do not correspond to its circle of
visibility. The images transmitted over the terrestrial digital
network 20 are the images that are not selected by the selection
module 11. In addition, these non-selected images are not stored by
the storage means 13 of this receiving station 50, 51, 52, 53,
54.
[0074] In FIG. 2 a satellite 1 which has accomplished the
acquisition of an image 21 of a portion of the terrestrial globe
transmits the acquired image 21 to a receiving station 50
represented schematically in FIG. 5. When this image 21 is received
by the receiving module of this receiving station 50, it is
transmitted to the selection module 11. This selection module 11
determines, for example by reading the header of the image 21, the
geographical zone that corresponds to this image 21, as well as the
period in which this image was captured by a satellite 1. In order
to do this, the selection module 11 includes means for reading the
header of each image received by the receiving module 10. The
selection module 11 then determines whether this image pertains to
the circle of visibility of this receiving station 50. This
determination is accomplished, according to this embodiment, by
accessing the memory 12 of this receiving station, which contains
the list of all the regions of the world for which this station is
competent. If receiving station 50 is competent for this image 21,
the selection module 11 orders the storage of the image 21 by the
storage means 13 of this station 50. On the other hand, if the
selection module 11 determines that receiving station 50 is not
competent for this image 21, it orders the placing of this image
onto the public digital network 20. Each station 51, 52 linked to
this digital network 20 then determines, when the image 21 reaches
it, whether or not said image pertains to its circle of visibility.
As soon as a receiving station determines that the image 21 is
returning to it, it stores said image by means of its storage means
13, otherwise it allows said image to circulate over the
terrestrial digital network 20.
[0075] In FIG. 3 a satellite 1 has accomplished the acquisition of
an image of a zone of the circle of visibility (represented by
dots) of receiving station 50. In this example the circle of
visibility of receiving station 50 defines a continuous region
around receiving station 50. This image is transmitted directly to
receiving station 50, which is therefore competent for this image.
Receiving station 50 will therefore store this image by means of
its storage means 13.
[0076] In FIG. 4 a satellite 1 has accomplished the acquisition of
an image of a zone of the circle of visibility of receiving station
54. FIG. 4 illustrates the case where the satellite 1 has not been
able to transmit the acquired image directly to the competent
receiving station 54 for this image. Such a case may occur, for
example, when receiving station 54 is out of order or in the
process of maintenance, or when receiving station 54 is already
about to receive an image emanating from another satellite, or when
receiving station 54 is no longer in the line of sight of the
satellite, etc. In such a case the satellite 1 transmits the image
to another receiving station 50, which is not competent for this
image. Since the selection module of this receiving station 50 has
not selected the received image, receiving station 50 transmits the
image over the terrestrial digital network. In FIG. 3 the image
successively transits receiving station 51, receiving station 52,
receiving station 53, in order to be recognised by receiving
station 54 and in this way to be backed up by the storage means 13
of receiving station 54.
[0077] As the acquisitions of images realised by the satellites
proceed, each receiving station constitutes a base of images that
are representative of its circle of visibility as defined by the
data appearing in its memory 12. Each image of this base of images
is defined, for example, by spatial coordinates and by a temporal
coordinate. These spatial and temporal coordinates are, according
to an advantageous embodiment, the data that appear in the header
of the image and that enable each selection module to determine
whether or not the image is within its competence. According to an
advantageous embodiment of the invention, one or more images
stemming from one or more sources may correspond to a triplet of
spatial and temporal coordinates. In particular, an instrument
according to this embodiment of the invention may include, besides
the satellites of the spatial layer, terrestrial cameras, such as
webcams, that are suitable to acquire an image and to transmit it
by means of the digital network 20 to a competent receiving
station, taking account of the spatial and temporal coordinates of
the image in question. An instrument according to the invention may
also include other devices for acquisition of images, which are
arranged on board other aircraft or even arranged at the top of
terrestrial buildings, such as apartment buildings, and can
transmit the acquired images to the receiving stations.
[0078] An instrument according to the invention enables any device
connected to the digital network 20 to access the receiving
stations and therefore the images stored in the storage means of
these receiving stations. According to an advantageous embodiment,
the images can be directly accessed by the Internet network, so
that any search engine can access an image of a given region. In
order to do this, the images can be archived with a name according
to a predetermined format that represents the spatial and temporal
coordinates of the image. Moreover, a user who is seeking an image
of a given region captured by an instrument according to the
invention does not need to know which receiving station is
accommodating the image that he/she is seeking. The distribution of
the images of the globe that are captured by an instrument
according to the invention among the various receiving stations is
transparent from the point of view of the person who is seeking an
image.
[0079] Advantageously, an instrument according to the invention
implements a process according to the invention. A process
according to the invention is advantageously implemented by an
instrument according to the invention.
[0080] According to other embodiments, an instrument according to
the invention acquires and downloads data other than images. In
addition, the target zone of the instrument may be a part of space,
a part of the terrestrial globe, etc. The characteristic data
enabling the acquired data to be distributed among the various
receiving stations may be of all types and may be based on a
characterisation that is intrinsic to the datum or intrinsic to the
acquisition instrument, etc.
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